“What if global warming is just a natural cycle?” This argument is, perhaps, one of the most common raised by the average person, rather than someone who makes a career out of denying climate change. Cyclical variations in climate are well-known to the public; we all studied the ice ages in school. However, climate isn’t inherently cyclical.

A common misunderstanding of the climate system characterizes it like a pendulum. The planet will warm up to “cancel out” a previous period of cooling, spurred by some internal equilibrium. This view of the climate is incorrect. Internal variability will move energy between the ocean and the atmosphere, causing short-term warming and cooling of the surface in events such as El Nino and La Nina, and longer-term changes when similar cycles operate on decadal scales. However, internal forces do not cause climate change. Appreciable changes in climate are the result of changes in the energy balance of the Earth, which requires “external” forcings, such as changes in solar output, albedo, and atmospheric greenhouse gases. These forcings can be cyclical, as they are in the ice ages, but they can come in different shapes entirely.

For this reason, “it’s just a natural cycle” is a bit of a cop-out argument. The Earth doesn’t warm up because it feels like it. It warms up because something forces it to. Scientists keep track of natural forcings, but the observed warming of the planet over the second half of the 20th century can only be explained by adding in anthropogenic radiative forcings, namely increases in greenhouse gases such as carbon dioxide.

Of course, it’s always possible that some natural cycle exists, unknown to scientists and their instruments, that is currently causing the planet to warm. There’s always a chance that we could be totally wrong. This omnipresent fact of science is called irreducible uncertainty, because it can never be entirely eliminated. However, it’s very unlikely that such a cycle exists.

What about an internal cycle, perhaps from volcanoes or the ocean, that releases massive amounts of greenhouse gases? This wouldn’t make sense either, not only because scientists keep track of volcanic and oceanic emissions of CO2 and know that they are small compared to anthropogenic emissions, but also because CO2 from fossil fuels has its own fingerprints. Its isotopic signature is depleted in the carbon-13 isotope, which explains why the atmospheric ratio of carbon-12 to carbon-13 has been going down as anthropogenic carbon dioxide goes up. Additionally, atmospheric oxygen (O2) is decreasing at the same rate that CO2 is increasing, because oxygen is consumed when fossil fuels combust.

A natural cycle that fits all these fingerprints is nearly unfathomable. However, that’s not all the cycle would have to explain. It would also have to tell us why anthropogenic greenhouse gases are not having an effect. Either a century of basic physics and chemistry studying the radiative properties of greenhouse gases would have to be proven wrong, or the natural cycle would have to be unbelievably complex to prevent such dramatic anthropogenic emissions from warming the planet.

It is indeed possible that multidecadal climate variability, especially cycles originating in the Atlantic, could be contributing to recent warming, particularly in the Arctic. However, the amplitude of the cycles simply can’t explain the observed temperature change. Internal variability has always been superimposed on top of global surface temperature trends, but the magnitude – as well as the fingerprints – of current warming clearly indicates that anthropogenic greenhouse gases are the dominant factor.

Despite all these lines of evidence, many known climatic cycles are often trumpeted to be the real cause, on the Internet and in the media. Many of these cycles have been debunked on Skeptical Science, and all of them either aren’t in the warming phases, don’t fit the fingerprints, or both.

For example, we are warming far too fast to be coming out of the last ice age, and the Milankovitch cycles that drive glaciation show that we should be, in fact, very slowly going into a new ice age (but anthropogenic warming is virtually certain to offset that influence).

The “1500-year cycle” that S. Fred Singer attributes warming to is, in fact, a change in distribution of thermal energy between the poles, not a net increase in global temperature, which is what we observe now.

The Little Ice Age following the Medieval Warm Period ended due to a slight increase in solar output (changes in both thermohaline circulation and volcanic activity also contributed), but that increase has since reversed, and global temperature and solar activity are now going in opposite directions. This also explains why the 11-year solar cycle could not be causing global warming.

As we can see, “it’s just a natural cycle” isn’t just a cop-out argument – it’s something that scientists have considered, studied, and ruled out long before you and I even knew what global warming was.

A very happy 2011 to everyone. I thought I would write a New Year’s post like last year’s.

ClimateSight wouldn’t exist at all without my very best friend and partner, who, after listening for months to my rambles about climate science and policy, set me up with a blog. Since my first post, he has listened to my ideas and provided many of his own, even though he’s not particularly interested in climatology. He is also a source of balance in my life, keeping me sane when news reports and nasty comments start to overwhelm me.

Equally deep gratitude goes to the scientist who first sparked my interest in climate, and who continues to be both a mentor and a friend, as well as a library (I promise I’ll return those books sooner or later). You know who you are!

I have received advice on everything from my comment policy to my course selection from many wise climate bloggers, such as Steve Easterbrook, Michael Tobis, and Tamino, as well as countless others who prefer to read and comment than to write their own blogs – too many to name!

This year, I have become involved in Skeptical Science, a multi-faceted collaboration of scientists and science enthusiasts concerned about the state of climate change communication. It is an honour to be part of the supportive, enthusiastic community of authors, and the articles they write provide hours of fascinating reading and further research.

Last but not least, I must thank the readers and commenters over here. I feel that I get more out of this blog than I put in. My thoughts on a topic don’t end when I hit “publish” – that’s just the beginning, as insights and links to further reading invariably appear in the comments.

I am grateful for more than the people who helped to create this online community, though. I am grateful to live in the age of information when looking up the state of Arctic sea ice takes less than a minute. I am grateful to live in the age of climatology, where the field is expanding throughout virtually every discipline. Finally, strangely enough, I am grateful to live in the age of climate change, to witness this fascinating phenomenon unfold, and (hopefully) to be a part of the generation that stops it in its tracks.

I apologize for my relative silence recently. I am in the midst of studying for my first set of final exams. To tide you over until that has calmed down a bit, I will share some of the interesting pieces I have read and watched recently.

John Cook from Skeptical Science has compiled his articles and rebuttals into a gorgeous document about the evidence for anthropogenic climate change, written in accessible language with effective graphics on every page. It’s so effective, I would like to print out a few dozen of these booklets and hand them out at the university.

On RealClimate, Ray Pierrehumbert addressed the common policy option of focusing on cutting emissions of methane and soot in the short-term in order to “buy us time” to reduce carbon dioxide. In fact, because these emissions have such a short atmospheric lifetime, it doesn’t really matter whether we focus on them now or later – while concentrations of carbon dioxide, with a lifetime of centuries to millennia, highly depend on when we address it. Take a look at these projections comparing our options:

Michael Tobis, however, thinks that we should focus on non-CO2 emissions despite these realities. Short-term economic and population “crashes” due to sudden warming in the near term could conceivably be more damaging to human security, because it means that we won’t be able to afford any mitigation, further worsening the long-term emissions. Both articles are worth a read.

I have really been enjoying the recent developments over at Skeptical Science, a dynamic site that is possibly the best example of climate science communication I have encountered, and to which I am proud to be a new contributing author!

It looks like John Cook, the creator of Skeptical Science, has been building a database of climate change links, everything from blog posts to newspaper articles to peer-reviewed papers, by everyone from Anthony Watts to Joe Romm to James Hansen. He’s also been keeping track of which common misconceptions appear the most and from which sources. Now you can subscribe to daily emails that include a dozen or so links from the database, organized and colour-coded according to source and bias. I’ve only been getting these emails for a few days, and they have already pointed me towards some fascinating articles I wouldn’t have had the time to seek out otherwise. (However, I can’t seem to stop Windows Live from putting them in my junk folder – any ideas?)

Skeptical Science has a great business relationship with Shine Technologies, the IT company that created Skeptical Science smartphone apps for free – simply because they care about the state of our climate. Now they’ve created a Firefox add-on that allows users to submit links to the database. If the page you’re on is already in the database, you can view, with one click of a mouse, which (if any) common misconceptions are in the article, complete with links to the ever-growing Skeptical Science rebuttal list. I haven’t tried this add-on yet, because I am a fan of Chrome, but it certainly looks very cool.

Skeptical Science has done a lot for my understanding of climate change. Early on, it was my first stop whenever I encountered a skeptic argument I was unfamiliar with, because I knew I could trust its citations and accountability. Now, I read the list of arguments and rebuttals just for fun, and to brush up my understanding. I love the new dynamic direction the site is taking, and I hope all of these projects continue and flourish.

I was recently honoured to join Skeptical Science, a comprehensive database of rebuttals to common climate change misconceptions, as an author. Here I am republishing my first article regarding the common myth that breathing out contributes to the buildup of atmospheric carbon dioxide. It is the Intermediate version, and I have also written a very similar Basic version, which includes a diagram by John Cook. Enjoy!

The very first time you learned about carbon dioxide was probably in grade school: We breathe in oxygen and breathe out carbon dioxide. Any eight-year-old can rattle off this fact.

More specifically, the mitochondria within our cells perform cellular respiration: they burn carbohydrates (in the example shown below, glucose) in the oxygen that we breathe in to yield carbon dioxide and water, which we exhale as waste products, as well as energy, which is required to maintain our bodily processes and keep us alive.

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

carbohydrates + oxygen → carbon dixoide + water + energy

It should come as no surprise that, when confronted with the challenge of reducing our carbon emissions from the burning of fossil fuels, some people angrily proclaim, “Why should we bother? Even breathing out creates carbon emissions!”

This statement fails to take into account the other half of the carbon cycle. As you also learned in grade school, plants are the opposite to animals in this respect: Through photosynthesis, they take in carbon dioxide and release oxygen, in a chemical equation opposite to the one above. (They also perform some respiration, because they need to eat as well, but it is outweighed by the photosynthesis.) The carbon they collect from the CO2 in the air forms their tissues – roots, stems, leaves, and fruit.

These tissues form the base of the food chain, as they are eaten by animals, which are eaten by other animals, and so on. As humans, we are part of this food chain. All the carbon in our body comes either directly or indirectly from plants, which took it out of the air only recently.

Therefore, when we breathe out, all the carbon dioxide we exhale has already been accounted for. By performing cellular respiration, we are simply returning to the air the same carbon that was there to begin with. Remember, it’s a carbon cycle, not a straight line – and a good thing, too!

I’ve really been enjoying the Advanced versions of Skeptical Science’s rebuttals to common misconceptions about climate change. So far, they have all been written by someone going by the name of dana1981, who I would like to give a huge shout-out to. I am a new B.Sc. student who is interested in pursuing a career in climate change research, and these articles have been very helpful in giving me a taste of basic atmospheric science.

In “How do we know more CO2 is causing warming?”, I was introduced to the relatively simple equation required to calculate the radiative forcing of increased atmospheric carbon dioxide, as well as the expected equilibrium temperature change from CO2, using the range of values for climate sensitivity provided by the IPCC (as calculating climate sensitivity is not quite so simple!)

In “The human fingerprint in global warming”, dana1981 discussed different attribution studies, and explained how anthropogenic warming has certain “fingerprints” – more warming at night than during the day, a cooling of the stratosphere, and a rise in tropopause height – all of which have been observed. I had a basic understanding of these fingerprints and why they occurred, but it was great to read about the current research in attribution studies, with impeccable citations.

“How sensitive is our climate?” was similar to the first article, but also addressed the common misconception that climate sensitivity is specific to different forcings. If the climate has low sensitivity to CO2, it also has low sensitivity to solar radiation, cosmic ray feedback, etc. The equilibrium temperature change doesn’t care if the extra few W/m2 is from the greenhouse effect or planetary albedo – it changes with the same speed either way, which disproves many skeptical arguments. Additionally, since the prehistoric record shows large swings in climate resulting from relatively small forcings, scientists are confident that climate sensitivity is not very low.

“Solar activity & climate: is the sun causing global warming?” was absolutely fascinating. The equations required to calculate solar forcing using total solar irradiance were new to me, and dana1981 went so far as to analyze early 20th-century warming, calculating how much was due to an upswing in solar irradiance and how much was due to anthropogenic greenhouse gases. During the latter half of the 20th century, solar irradiance has dropped back down, but warming has only accelerated.

Skeptical Science’s recent efforts to expand their rebuttals to include beginner, intermediate, and advanced levels of explanation were inspired by a RealClimate post written by Dr. Gavin Schimdt. He thoughtfully wrote,

I think we should be explicitly thinking about information levels and explicitly catering to different audiences with different needs and capabilities. One metaphor that might work well is that of an alpine ski hill. There we have (in the US for instance) green runs for beginners wanting a gentle introduction and where hopefully nothing too bad can happen. Blue runs where the technical level is a little more ambitious and a little more care needs to be taken. Black expert runs for those who know what they are doing and are doing it well, and finally, double black diamond runs for the true masters. No-one accuses ski resorts of being patronising when they have green runs interspersed with the more difficult ones, and neither do they get accused of elitism when one peak has only black runs going down (as I recall all too painfully on my first ski outing). People self-segregate and generally find their way to the level at which the feel comfortable – whether they want a easy or challenging ride – and there is nothing stopping them varying the levels as their mood or inclination takes them.

Skeptical Science took up this challenge, and although their efforts have largely been focused on creating “plain-English” beginner articles, as a huge target audience for climate change communication is the general public, I’m extremely grateful that they’re also catering to new science enthusiasts such as myself with the advanced articles. Please, keep them coming!

While we’re on the topic, I should also mention a great new post by Skeptical Science, which is not part of their argument database – “The contradictory nature of global warming skepticism”. You can’t hold the objection that the world isn’t warming and then turn around and say that global warming is natural, but these and other self-disproving arguments reach us on a daily basis. Deniers can’t seem to agree on a single unified objection to anthropogenic global climate change, and some individuals, as the post shows, contradict themselves up to five times in six months.

And hey, I just realized right now – that post was also written by dana1981. Whoever this writer is, he or she is doing a great job.

About

Kaitlin Alexander is a PhD student in climate science at the University of New South Wales in Sydney, Australia. She became interested in climate science as a teenager on the Canadian Prairies, and increasingly began to notice the discrepancies between scientific and public knowledge on climate change. She started writing this blog at age sixteen to help address this gap in public understanding, and it slowly evolved into a record of her research as a young climate scientist. Read more

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